Scientists sequence genomes of Antarctic fish
The sequenced genomes reveal that notothenoids split off from other species more recently than previously thought.
An international team of researchers has successfully sequenced the genomes of 24 species of notothenioids, providing clues to how they have evolved to survive in the cold of the Southern Ocean.
The scientists, including experts from the University of Cambridge and the Wellcome Sanger Institute in the UK, used the latest long-read technologies to sequence the genomes of notothenioids, the dominant fish group in the Southern Ocean.
Notothenioids live below the ice in Antarctica, isolated from much of the wider marine world owing to the Antarctic Circumpolar Current, which extends as deep as the seafloor and makes it nearly impossible for fish to migrate to and from Antarctica.
The research revealed that notothenioids split off from other species approximately 10.7 million years ago, more recently than previously thought.
It was also found that the length of the genome has doubled in the species of notothenioids, such as the family Channichthyidae, that specialise in surviving extreme cold. The increase in genome size is due to a greater number of genomic elements known as transposons. These elements can copy themselves into new positions within the genome and potentially introduce new functions.
Notothenioids of the Channichthyidae family, which can survive in water as cold as -2°C, do not have oxygen-binding haemoglobin proteins, making them the only known vertebrates not to have red blood cells. The high oxygen solubility of the water in the Southern Ocean allows them to survive with a much reduced capacity to carry oxygen in their blood.
Professor Richard Durbin, senior author of the research, said: “Notothenioid fish live at the edge of viability. Sequencing a broad collection of their genomes gives insights into how they have evolved to survive there, and supports our understanding of a critical ecosystem. This study is a great example of how advances in genomics are revolutionising our ability to understand biodiversity across the world.”
The study, ‘Genomics of cold adaptations in the Antarctic notothenioid fish radiation’, has been published in Nature Communications.
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